The primary goal of this project is to determine how and why certain forms of behavior develop, change, and persist in the presence of certain classes of stimuli, when these stimuli serve as reliable signals for other environmental events. The project has previously focused on the phenomenon of sign-tracking, which involves the tendency of animals (a) to orient toward, approach, and often contact localizable and reliable signals of imminent Pavlovian appetitive reinforcers (USs) and (b) to withdraw from signals of nonreinforcement. In this connection we have been and are studying (1) spatial, temporal, and "predictive" relations between CSs, USs, and intertrial intervals, (2) specific properties of CS and US (salience, intensity, localizability, modality, motivational aspects, etc.), (3) the influence of different positive or negative response-reinforcer contingencies, and (4) various response components and measures (orienting, approach-withdrawal, contact of CS and US). Experiments also examine the intimate role of sign-tracking in positive conditioned suppression and in the feature-positive superiority found during discrimination learning. Planned work involves: an analysis of directed movements controlled by signals of aversive USs (e.g., shocks); the development of detection techniques for assaying "backward association" formation in pigeons; an examination of the applicability of Gestalt laws of perceptual organization for the definition of a "feature" or "sign"; the investigation of rehearsal processes in pigeons receiving unexpected reinforcement or nonreinforcement. BIBLIOGRAPHIC REFERENCES: Hearst, E. Pavlovian conditioning and directed movements. In G. Bower (Ed.), The psychology of learning and motivation (Vol. 9). New York: Academic Press, 1975. Pp. 215-262. Hearst, E., & Gormley, D. Some tests of the additivity (auto-shaping) theory of behavioral contrast. Animal Learning and Behavior, 1976, in press.